Metering and distributing device for fuel injection systems



G. STUMPP Nov. 3, 1970 METERING AND DISTRIBUTING DEVICE FOR FUEL INJECTION SYSTEMS Filed Nov. 22; 1968 United States Patent Int. Cl. BtlSb 1/30 US. Cl. 239-533 Claims ABSTRACT OF THE DISCLOSURE A unitary device for metering fuel and distributing the same to injection valves of an internal combustion engine, said device includes a control plunger for varying synchronously flow passage sections associated with each injection valve to provide uniform metering of the fuel and a plurality of piston-cylinder assemblies, one associated with each injection valve, the piston of each said assembly controls the admission of fuel to its associated valve in response to the pressure fluctuations upstream of said synchronously variable flow passage sections to ensure a constant difference between the pressures upstream and downstream of said sections.

BACKGROUND OF THE INVENTION This invention relates to a metering'and' distributing device for continuously operating fuel injection systems used in particular in multicylinder internal combustion engines having distributing means and metering means which, in the case of an at least approximately constant pressure drop determines, by varying an adjustable flow passage section, the fuel quantities to be injected.

Devices of this type purport to provide for an exact metering of the fuel corresponding to the operating conditions of the internal combustion engine and for a uniform distribution of the fuel into the individual cylinders of the engine.

A device of the aforenoted type is disclosed in British Pat. No. 1,066,721 wherein the fuel is metered at a sole flow passage section by means of an arbitrarily displaceable needle. A constant pressure drop is maintained by means of a throttle element disposed upstream of said section. The throttle element is affected, on the one hand, by the fuel pressure downstream of the flow passage section and, on the other hand, by the pressure between the throttle element and the flow passage section. The fuel is distributed to the individual cylinders subsequent to metering by means of a distributor operating with throttles.

The afore-outlined device is disadvantageous in that the pressure drop at the distributing throttles is formed by the difference between two high pressures and therefore it is strongly dependent on the changes in the injection pressure or in the delivery pressure that advances fuel to the distributor. Furthermore, the separate arrangement of the metering device and the distributor requires relatively expensive conduit systems.

OBJECT AND SUMMARY OF THE INVENTION I fuel injection valve there is associated a first variable flow passage section synchronously controlled by a plunger and a second variable flow passage section each controlled by a separate piston exposed to opposed pressures 3,537,654 Patented Nov. 3, 1970 upstream and downstream of said first variable flow passage sections.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic representation of the principles of the invention;

FIG. 2 is a cross-sectional view of a preferred embodiment; and

FIG. 3 is a sectional view along line III-III of FIG. 2.

DESCRIPTION OF THE EMBODIMENT Turning now to FIG. 1 schematically showing the principles in structure and operation of the invention, the fuel is delivered by supply conduit 1 to a longitudinal bore 2 from which extend branch channels 3a. The flow passage sections 4 of these branch channels are variable by a common control plunger '5 slidably disposed in bore 2. Each branch channel 3a merges into a separate cylinder 6 in which there is arranged a piston 7 which, at its outer face, is exposed to the pressure prevailing in bore 2 and thus in the supply conduit 1 and, at its inner face, is exposed to the pressure in the respective branch channel 3a. The latter pressure is aided by the force of a compression spring 8. Each piston 7 controls a second flow passage section 9 associated With each branch channel 3b connecting cylinder 6 with an injection valve 30.

Turning now to the embodiment illustrated in FIGS. 2 and 3, bushing sleeves 10 and 11 inserted in axial alignment into a housing block 12 define a longitudinal bore 2'.

The fuel supply conduit 1' merges radially into bore 2' and is in continuous communication with an annular circumferential groove 13 provided in the lateral face of a control plunger 5 slidably held in bore 2. One axial terminus of annular groove 13 defines a control edge 14 for varying flow passage sections 4' (only one shown), each formed in the bushing sleeve 10 by a narrow longitudinal slot 15. The circumferential annular groove 13 also serves to equalize the pressures on control plunger 5'. The slots 15 are of identical Width and all begin at the same height by starting from the frontal edge of bushing sleeve 10. These slots may be very accurately made with relatively inexpensive means. The frontal edge of bushing sleeve 10 is sealed by the abutting front edge of the bushing sleeve 11.

Each slot 15 continues in a branch channel 3a merging into a cylinder 6'. The exemplary embodiment shown in FIG. 2 comprises four cylinders 6 equidistantly arranged about longitudinal bore 2'. In each cylinder 6 there is slidably disposed a piston 7 formed preferably as a shell to minimize its mass. Each piston 7' controls a second flow passage section 9 continuing in a branch channel 3b connecting each cylinder 6' with a fuel injection valve (not shown in FIGS. 2 and 3).

The annular groove 13 of control plunger 5' is in continuous communication with ports 16 provided in bushing sleeves 11 and admitting the fuel delivery pressure prevailing in supply conduit 1 (Le. the pressure upstream of flow passage section 4) to the outer face of each piston 7'. The inner face of each piston 7' is exposed to the pressure prevailing in branch channel 3a (i.e. the pressure downstream of flow passage section 4).

The cylinders 6' are closed by means of screw caps 18. Between the cap 18 and piston 7' there is disposed in each cylinder 6' a compression spring 8' urging the piston 7' towards the longitudinal bore 2' and thus aiding the pressure on the inner face of each piston 7.

The longitudinal bore 2' is closed by a plug 19. The control plunger '5' is provided with an axial bore 20 for the discharge of fuel leaking into bore 2' beyond the control plunger 5'.

3 OPERATION OF THE EMBODIMENT Referring now simultaneously to FIGS. 1, 2 and 3, the afore-described fuel metering and distributing device operates as follows:

The fuel is, by virtue of the setting of the control plunger 5, metered identically for each branch channel 3a, 3a. Stated in other terms, the flow passage section 4, 4 (F) and the fuel quantity (Q) passing thereacross changes according to the formula Q zQ F zF at constant difference of the pressures upstream and downstream of the controlled flow passage section 4, 4'.

A constant difference between the pressures upstream and downstream of the flow passage sections 4, 4 is maintained in the following manner: Should the pressure increase in the supply conduit 1 1' (i.e. upstream of the flow passage sections 4, 4), the pistons 7, 7 are urged radially away from bore 2, 2', thus narrowing the flow passage sections 9, 9'. Consequently, the pressure in cylinders 6, 6' and in branch channels 3a, 3a (i.e. downstream of fiow passage sections 4, 4') also increases resulting in the maintenance of the original differential pressure. Conversely, should the pressure upstream of the flow passage sections 4, 4' decrease, the pistons 7, 7', by virtue of their responsive radial shift towards bore 2, 2, enlarge the flow passage sections 9, 9'. As a result, the pressure downstream of flow passage sections 4, 4' also decreases. It is thus seen that by virtue of the control of flow passage sections 9, 9 by means of pistons 7, 7', the quantity of fuel in branch channels 3b, 3b remains unaffected by pressure fluctuations in cylinders 6, 6', since with increasing pressure therein, the fiow passage sections 9, 9' are accordingly narrowed preventing the fuel quantity passing through branch channels 3b, 3b from increasing in response to the augmented pressure.

A particular advantage achieved by the inventive device resides in a very accurate dosing of the injected fuel quantities which is made possible because, first, the distributing device and the metering device are connected in parallel and form a unit and, secondly, the control of the pressure drop at the individual flow passage sections 4, 4' is effected independently from one another. The simple synchronous setting of the fiow passage sections 4, 4 by means of control plunger 5, 5 is a further advantage of the invention. Further, the injected quantity at each fuel injection valve is substantially independent of the delivery pressure that forces the fuel to the device and of the injection pressure of the individual fuel injection valves. Consequently, less expensive fuel injection valves may be used. The pressure in the supply conduit may be relatively low. Pressure fluctuations in the fuel injection conduit have, by virtue of the aforenoted arrangement of the flow passage sections 9, 9' downstream of the sections 4, 4', practically no effect on the metering of the fuel. By virtue of the arrangement of the individual elements of the device, less parts are necessary than if a correspondingly accurate distributor is arranged downstream of the metering device. At the same time, with the aforedescribed arrangement the smallest possible variable volume may be obtained in the injection circuit so that, also considering the small moment of inertia of the displaceable pistons, a maximum setting speed may be achieved.

That which is claimed is:

1. Fuel metering and ditsributing device for a continuously operating fuel injection system having a plurality of injection valves each associated with a cylinder of a multi-cylinder internal combustion engine, said device comprising,

(A) first branch channels, one associated with each said injection valve,

(B) a first flow passage section provided in each of said first branch channels,

(C) supply means for simultaneously delivering fuel under pressure to each of said first branch channels through said first flow passage sections,

(D) common means for varying in unison each of said first flow passage sections,

(E) second branch channels, each establishing communication between an injection valve and a first branch channel associated therewith,

(F) a second flow passage section provided in each of said second branch channels, and

(G) separate means associated -with each said second flow passage section for individually varying the latter to maintain substantially constant the difference between the fuel pressures upstream and downstream of said first flow passage sections.

2. A device as defined in claim 1, including a longitudinal bore containing all of said first flow passage sections; said supply means comprising a conduit merging into said bore; said common means is formed of a control plunger slidably disposed in said bore.

3. A device as defined in claim 2, wherein said control plunger is provided with a circumferential annular groove, said conduit is in continuous communication therewith, one terminal of said groove is provided with a control edge to vary in unison said first flow passage sections in communication -with said groove.

4. A device as defined in claim 2, wherein each said first fiow passage section is formed of a narrow, elongated slot.

5. A device as defined in claim 4, wherein said bore is defined by two abutting, axially aligned bushing sleeves; said slots are of identical width and extend in one of said bushing sleeeves from a terminal edge thereof.

6. A device as defined in claim 5, wherein said terminal edge is in sealing abutment with the other of said bushing sleeves.

7. A device as defined in claim 1, wherein said first branch channnels and said second branch channels associated with the same injection valve are interconnected by means of a cylinder, said separate means is formed of a piston slidably held in each of said cylinders; each of said cylinders contains one of said second flow passage sections adapted to be varied by said piston.

8. A device as defined in claim 7, wherein each said piston has an inner and an outer face, each cylinder is provided with an opening to establish continuous communication between said supply means and said outer face of each piston, the position of said pistons is determined, on the one hand, by the fuel pressure downstream of said first flow passage sections and affecting said inner face of said pistons and, on the other hand, by the fuel pressure upstream of said first flow passage sections and affecting said outer face of said pistons.

9. A device as defined in claim 7, wherein each said piston has a shell-like configuration.

10. A device as defined in claim 8, wherein the fuel pressures downstream of said first flow passage sections are aided by spring means disposed in each said cylinder and engaging said inner face of said pistons.

References Cited UNITED STATES PATENTS 1,973,215 9/1934 Lyman 239533 2,706,520 4/1955 Chandler 239-533 X 2,852,308 9/1958 Whitson 239-- X LLOYD L. KING, Primary Examiner US. Cl. X.R. 239--453 

